Many types of low and medium voltage switchgear systems use power circuit breakers that can be withdrawn for maintenance or for replacement. Power circuit breakers from various manufacturers may not be interchangeable. This leads to a two different problems. One, as the manufacturers eliminate older products and introduce new technologies, the new products have not maintained compatibility with existing switchgears. Secondly, there are no compatible solutions that allow the switchgear panel from one manufacturer to adapt to the circuit breaker from another manufacturer.
The result is that many switchgear installations have power circuit breakers that are costly or impractical to maintain. Complete replacement of switchgear is very expensive and involves significant downtime. In the past, upgrading of obsolete circuit breakers was accomplished by significantly modifying a new circuit breaker to fit into the existing switchgear panel or by modifying the switchgear panel to accept a new breaker.
A retrofitting solution for circuit breaker can involve an extensive engineering to match the existing panel specification with the contacts of a new circuit breaker. This can involve obtaining a wiring diagram for the electrical operation of the breaker, actual dimensions of the original breaker where elevation drawings could be needed, and information and drawings for mechanical interlocks, primary and secondary disconnects, and auxiliary switch operators. This method can be cumbersome as a custom made solution is made for each of the panel.
Another known retrofitting approach is based on adapting a new replacement breaker cradle to the existing switchgear cell by using a “module” or “cradle-within-a-cradle” approach. For example, U.S. Pat. No. 7,124,488 is directed to a system for modifying a circuit breaker for removable installation in a cell of switchgear system, wherein the unmodified circuit breaker is not adapted for mounting in the cell. The system described herein includes an adapter frame to which the circuit breaker is mounted and gear assemblies mounted to opposing sides of the circuit breaker. The gear assemblies adapt a racking device of the circuit breaker so as to be operable to rack the circuit breaker within the cell of the switchgear system. In this method there is rigidity in the design, as only certain panels meeting the dimensions of module can be retrofitted. This also can involve inserting, connecting and supporting the new module or cradle to existing primary and secondary parts inside the switchgear.
Another alternative approach is the “roll in replacement” technique where the existing circuit breaker with truck or cassette, interlocks and wiring is replicated in the new breaker provided with retrofit solution. U.S. Pat. No. 7,544,907 is one exemplary disclosure that utilizes this technique, as this patent discloses a retrofit assembly structured to allow a CM22 type circuit breaker to engage, and be enclosed by, a CMD type circuit breaker tank. The retrofit assembly includes a levering mechanism, a circuit breaker bus assembly having bus support members, and a door handle system structured to allow a user to actuate the circuit breaker contacts when the tank is closed.
These approaches can involve additional space limitations that complicate dielectric and heat run considerations.
Thus the known approaches of custom designing the circuit-breaker or creating a new module with interlocking and auxiliary contact functions, both involve extensive custom design work and materials, and do not provide an optimum retrofitting solution.
It would therefore be desirable to improve the existing retrofit solutions to minimize the reduced assembly operation times and improve flexibility to allow a new circuit breaker to fit into any switchgear panel irrespective of the make and manufacture of the panel.